Seismic isolation reduces the induced seismic loads, particularly in low- to
medium-rise buildings, by avoiding resonance, with the predominant frequencies
of earthquake excitations, thanks to flexibility introduced at the isolation level.
This earthquake resistant design approach significantly decreases the shear
forces, interstory deflections, and floor accelerations of a building, avoiding
damage of its structural and non-structural elements as well as damage of its
contents. The size of the seismic gap, which must be provided around a
seismically isolated building, in order to facilitate the expected large relative
displacements at the isolation level, is usually finite, due to practical limitations,
giving rise to the possibility of poundings of the building with adjacent structures
during strong earthquakes. Therefore, understanding how the effectiveness of
seismic isolation is affected from potential poundings of seismically isolated
buildings with adjacent structures due to strong ground motions is vital. This
research work aims to address this issue using numerical simulations and
parametric studies in an effort to investigate how the maximum floor
accelerations, story shear forces and interstory deflections of these buildings are
affected by impacts and the relevant design parameters and conditions.
Numerical simulations demonstrate that poundings may substantially increase
floor accelerations, especially as the stiffness of the impact is increased, and,
hence, may cause damage to the contents of a seismically isolated building,
significantly reducing the effectiveness of seismic isolation. In addition to the
presentation of results from parametric studies for some of the influencing
conditions, the possibility of using bumpers, as a practical measure to mitigate
the adverse effects from potential poundings, is considered.
Keywords: seismic isolation, poundings, impacts, seismic gap, bumpers.